Title: Physics of increased edge electron temperature and density turbulence during ELM-free QH-mode operation on DIII-D

Abstract

Here, we report increased edge electron temperature and density turbulence levels ($$\tilde{T}_e$$ and $$\tilde{n}_3$$) in Edge Localized Mode free Quiescent H-mode (ELM-free QH-mode) plasmas as compared to the ELMing time period. ELMs can severely damage plasma facing components in fusion plasma devices due to their large transient energy transport, making ELM-free operation a highly sought after goal. The QH-mode is a candidate for this goal as it is ELM-free for times limited only by hardware constraints. It is found that the driving gradients decrease during the QH-mode compared to the ELMing phase, however, a significant decrease in the ExB shearing rate is also observed that taken together is consistent with the increased turbulence. These results are significant as the prediction and control of ELM-free H-mode regimes are crucial for the operation of future fusion devices such as ITER. The changes in the linear growth rates calculated by CGYRO [Candy et al., J. Comput. Phys. 324, 73 (2016)] and the measured ExB shearing rate between ELMing and QH-mode phases are qualitatively consistent with these turbulence changes. Comparison with ELMing and 3D fields ELM suppressed H-mode finds a similar increase in $$\tilde{T}_e$$ and $$\tilde{n}_3$$, however, with distinctly different origins, the increased driving gradients rather than the changes in the ExB shearing rate in 3D fields ELM suppressed the H-mode. However, linear gyrokinetic calculation results are generally consistent with the increased turbulence in both ELM-controlled discharges.

Authors:

Sung, C. ^[1]; Rhodes, T. L. ^[1]; Staebler, G. M.  ^[2];

• Search DOE PAGES for author "Staebler, G. M."
• Search DOE PAGES for ORCID "0000-0002-1944-1733"

Yan, Z. ^[3]; McKee, G. R. ^[3]; Smith, S. P.  ^[2];

• Search DOE PAGES for author "Smith, S. P."
• Search DOE PAGES for ORCID "0000-0003-1526-380X"

Osborne, T. H. ^[2]; Peebles, W. A. ^[1]

---

+ Show Author Affiliations

1. Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy
2. General Atomics, San Diego, CA (United States)
3. Univ. of Wisconsin-Madison, Madison, WI (United States). Dept. of Engineering Physics

Publication Date:

Mon Mar 19 00:00:00 EDT 2018

Research Org.:

General Atomics, San Diego, CA (United States); Univ. of California, Los Angeles, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1540159

Alternate Identifier(s):

OSTI ID: 1426849

Grant/Contract Number:  

FC02-04ER54698; FG02-08ER54984

Resource Type:

Accepted Manuscript

Journal Name:

Physics of Plasmas

Additional Journal Information:

Journal Volume: 25; Journal Issue: 5; Journal ID: ISSN 1070-664X

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

70 PLASMA PHYSICS AND FUSION TECHNOLOGY; physics